Succinate is known to build up in anaerobic conditions. For example, diving animals, hypoxic areas at the centre of tumours, and certain parasites can be observed to show elevated succinate in conditions of hypoxia. However, these studies are typically in the context of attempting to kill cells or to block or remove the cells from the system under study. Moreover, these systems are not always comparable the conditions experienced by mammalian cells under hypoxia. For example, in bacteria the two enzymatic activities involved in succinate metabolism are present in two separate enzymes [rather than in the same single enzyme succinate dehydrogenase (SDH) in mammalian cells].
Succinate has been studied in certain in vitro systems. It is possible that reactive oxygen species (ROS) generation via succinate has been observed in certain in vitro systems. However, such observations have been largely regarded as in vitro curiosities rather than a genuine reflection of possible conditions in vivo.
Succinate has been studied for oxygen sensing applications. There have been attempts to block the succinate in order to try to achieve an anti-inflammatory effect in the prior art.
There is no known experimental connection in the prior art linking succinate accumulation in vivo to ROS production by mitochondrial complex I due to succinate oxidation upon reperfusion.
Hu et al, Journal of Huazhong University of Science and Technology, Medical Sciences, vol. 25, 2005, pages 439-441 and Hirata et al, Transplantation, vol. 71, 2001, pages 352-359 have both shown that chemical preconditioning using 3-nitropropionate reduced ischemia-reperfusion injury in rats. The compound 3-nitropropionate is an inhibitor of mitochondrial complex II. Wojtovich et al, Basic Research in Cardiology, vol. 104, 2009, pages 121-129 have reported that the complex II inhibitor atpennin A5 protects the heart against simulated ischemia-reperfusion injury through a mKATP channel dependent mechanism. However, inhibitors such as 3-nitropropionate and atpennin A5 have the disadvantage that they are irreversible. As a consequence, any complex II that binds to such irreversible inhibitors is permanently prevented from carrying out its normal function.
Drose et al, Molecular Pharmacology, vol. 79, 2011, pages 814-822 studied several cardioprotective complex II inhibitors including 2-thenoyltrifluoroacetone (TTFA), 3-nitropropionate, atpennin A5 and malonate. Of the inhibitors tested, malonate required the highest concentration, in millimolar levels, to achieve half-maximal inhibition compared to nanomolar levels required for atepennin A5. In addition, malonate has the disadvantage that it is not cell-permeable. The other inhibitors TTFA, 3-nitropropionate and atpennin A5 have the disadvantage that they are irreversible.
Dimethylmalonate is a known compound. Malonate and its derivatives are industrial compounds used as feed stocks for polymer formation. There is no known teaching in the prior art for use of malonate derivative, such as dimethylmalonate, as a prodrug of an inhibitor of SDH. The prodrug dimethyl malonate will be hydrolysed in vivo to malonate which is an inhibitor of SDH.
The present invention seeks to overcome problem(s) associated with the prior art.